The anodization of metals into electrical insulators is a very attractive method of creating a gate dielectric for thin film transistors (TFT). Due to the self-limiting mechanism in the anodization process, the uniformity of thickness is guaranteed. Therefore, it is very easy to scale the anodization process to large substrates. The anodization process can be carried out in a typical ambience without the need for a vacuum and anodization solutions are inexpensive electrolytes. Further, the equipment cost and the operating cost of anodization is very low. While it is a challenge to make the anodized gate dielectric work for a-Si or Poly-Si due to their covalent natures, the process works very well for MOTFTs because of the ionic nature of metal oxide.
However, there are some disadvantages for anodized gate dielectrics. For example, in active matrix backpanels and the like to carry out the anodization process, all electrodes have to be connected together and to an external power supply. But in any large matrix design, the gate electrodes of different TFTs generally are isolated from each other. Therefore, a cut process is needed to provide the necessary isolation. When the cut process is performed, for example by photolithography, an extra mask and an extra etch step are introduced. These extra steps can substantially increase the complication and work in performing the anodization process. Also, vias are needed to connect the gate metal to subsequent metal layers to complete various circuits in the active matrix. Again, the formation of vias can substantially increase the complication and work in performing the connection process.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved process for anodizing gate metal in metal oxide thin film transistors (MOTFT) in large matrices to form the gate dielectric.
It is another object of the present invention to provide a new and improved process for fabricating an active matrix backpanel for LCD displays.